Smoking rates among individuals with depression are disproportionately higher than the general population, as are their rates of tobacco-related morbidity and mortality. The majority of psychiatric hospitals ban smoking on hospital grounds, thus providing an opportunity for inpatients to experience abstinence. Yet, smokers in inpatient psychiatric settings are rarely encouraged to quit and the vast majority return to smoking immediately after discharge. An effective intervention that targets this transition, capitalizing o this valuable experience of abstinence, is needed to increase smoking cessation in this at-risk population. The goal of the proposed study is to develop a mindfulness smartphone intervention with contingency management (MSI-CM) for smoking cessation that can be readily available to depressed smokers transitioning to their natural environment following psychiatric hospitalization. The goal will be accomplished by pursuing three specific aims: 1) to develop and conduct a preliminary pilot test (n=10) of the MSI-CM receiving inpatient psychiatric treatment, 2) to conduct a preliminary randomized controlled trial (RCT) with 60 depressed smokers recruited during inpatient psychiatric treatment, comparing MSI-CM and enhanced brief advice (E-BA), with a prediction that MS-CM relative to E-BA will result in higher rates of smoking cessation at 2-week, 4-week, and 3-month post-discharge follow-ups and have longer periods of continuous abstinence after hospital discharge, and 3) to examine MSI-CM's effects on key mechanisms (hypothesized mediators) and their associations with smoking outcomes at 2-week, 4-week, and 3-month follow-ups. The research proposed is innovative in that: 1) no previous studies have implemented a mindfulness intervention targeting tobacco use among depressed smokers in a psychiatric inpatient setting or have utilized smartphones to facilitate implementation, 2) the proposed intervention targets a neglected period of inpatient-home transition, with intervention components delivered in the context of both the inpatient setting and the patient's own environment, 3) the proposed intervention differs from existing mindfulness interventions in that smokers will practice mindfulness while abstinent and experiencing withdrawal, craving and negative affect, both in the hospital and in their own environment, incentivized by contingency management, 4) the use of contingency management (to reinforce abstinence) in conjunction with mindfulness training, in order to enhance the efficacy of mindfulness intervention for smoking cessation is innovative, and 5) no previous study has collected ecological momentary assessment data on constructs related to smoking and mindfulness in this high-risk population, in both an inpatient setting and after hospital discharge If this intervention is found to be efficacious, the potential impact of this program of research wll be considerable, not only in its innovation, but because its objectives are consistent with a significant public health priority: the ready dissemination of effective, low-cost interventions to reduce morbidity and mortality among individuals with psychiatric disorders.